The invention concerns an adhesive applicator for a labeling machine and consisting of an adhesive roller, especially one with a resilient surface, of an adhesive-supply mechanism, of an adhesive doctor positioned behind the supply mechanism in relation to the direction that the roller rotates in, and of a label getter with an adhesive-pickup surface that is in particular rigid and that rolls over the surface of the adhesive roller.
Adhesive applicators of this type are known (German patent No. 3 113 980). The adhesive roller generally has a resilient surface that rotating or rocking metal adhesive pallets roll over to pick up adhesive to apply to the labels. The applicators can be equipped with either a single adhesive doctor that ensures a uniform layer of adhesive over the total height of the adhesive roller or with two adhesive doctors. If there are two adhesive doctors, the one that is upstream in relation to the direction of rotation is designed as a preliminary doctor and the downstream doctor as a flow-metering doctor. The latter design allows layers of different thicknesses to be applied over the total height of the adhesive roller with a single segmented doctor. Adhesive layers of different thicknesses are desirable when different types of label, foil and paper for instance, are to be applied to an article.
All of these adhesive applicators are subject to malfunction as the result of labels being accidentally applied to the adhesive roller by the transfer mechanisms, the adhesive pallets for example. The labels, specifically, get jammed up upstream of the adhesive doctor, not only making it impossible to establish the desired thickness of the layer of adhesive but also causing the adhesive roller to heat up due to friction and hence to wear prematurely. Attempts have been made in many ways to eliminate these causes of malfunction.
The adhesive roller in one known applicator has continuous grooves around it with belts extending through them. The belts travel over a deflection mechanism positioned parallel to and at a distance from the adhesive roller. A comb engages between the free-running belts in the space between the adhesive roller and the deflection mechanism, and lifts off the defective labels transferred to the adhesive roller and advanced by the belts. This type of adhesive applicator is relatively expensive.
The adhesive roller in one known embodiment has a steel surface. The surfaces of the transfer mechanisms, the adhesive pallets for instance, are covered with a resilient material. It is difficult to fabricate a surfacing of this type that is precise enough to ensure non-slip roll-over, especially because pallets have to have recesses for the gripper mechanisms. Narrow webs are left in the vicinity of these recess, and it is difficult to fasten them permanently to their metal supports.